Synthesis and complexation of a new vic-dioxime ligand

Article abstract of DOI:10.1007/PL00010303

A new vic-dioxime ligand, N,N′-bis-(8-salicylideneimino-1-naphthyl)-diaminoglyoxime, has been synthesized from anti-dichloroglyoxime and 1-amino-8-salicylideneiminonaphthalene which has been prepared via the condensation product of 1,8-diaminonaphthalene

Full text of DOI:10.1007/PL00010303

Monatshefte fuÈr Chemie 131, 175±180 (2000)
Synthesis and Complexation of a New
vic-Dioxime Ligand
Ã
È
Æ
Esin Hamuryudan, Zehra A. Bayꢀ r, and Ozer Bekaroglu
Ç
Department of Chemistry, Technical University of Istanbul, TR-80626 Maslak, Turkey
Summary. A new vic-dioxime ligand, N,N0-bis-(8-salicylideneimino-1-naphthyl)-diaminoglyoxime,
has been synthesized from anti-dichloroglyoxime and 1-amino-8-salicylideneiminonaphthalene
which has been prepared via the condensation product of 1,8-diaminonaphthalene and
salicylaldehyde. The vic-dioxime ligand forms trinuclear complexes with Cu(II), Ni(II), Co(II),
and Pd(II). The uranyl complex of this ligand has a 2:1 metal-ligand ratio and a binuclear structure
with ꢀ-hydroxo bridges.
Keywords. Schiff base; vic-Dioxime; Complexation.
Introduction
Metal complexes of vicinal dioximes have been widely investigated as analytical
reagents [1] and models for biological systems [2], such as vitamin B12. The
columnar stacking of the compounds is thought to be the reason for their
semiconducting properties [3] and their behaviour in macrocyclization reactions
[4]. The exceptional stability and unique electronic properties of these complexes
can be attributed to their planar structure which is stabilized by hydrogen bonding
[5]. Another rapidly emerging area of chemical interest in recent years is the
synthesis of heterobi- or -trinucleating ligands and the coordination chemistry of
heteronuclear complexes of such ligands [6].
The coordination chemistry of Schiff bases derived from o-diamines and
salicylaldehyde has been the subject of many studies, and the oxygen-carrying
properties of some of these complexes are of considerable current interest due to
the obvious implications to complicated biological systems [7,8].
We have long been interested in the chemical behaviour of complexes
containing a planar MN4 core structure and additional donor sites with
phthalocyanines or vic-dioximes with the central coordination moiety and crown
ethers [9,10], N2O2 macrocycles [11±13], seven-membered heterocyclic ligands
[14], and S2O2 groups [15] as peripheral groups. In the present paper the synthesis
of a new vic-dioxime ligand containing two naphthalene groups with the aim of
obtaining tri- and tetranuclear complexes is presented.
Ã
Corresponding author

176
E. Hamuryudan et al.
Results and Discussion
The condensation reaction of 1,8-diaminonaphthalene and salicylaldehyde was
carried out in absolute ethanol at 60±65ꢀC, and the new Schiff base ligand 1-amino-
8-salicylideneimino-naphthalene (1) was isolated as yellow needles in good yield.
A new vic-dioxime ligand, N,N0-bis-(8-salicylideneimino-1-naphthyl) diamino-
glyoxime (2) was then prepared by a one-step reaction of E,E-dichloroglyoxime
(DCGO) and 1. Excess of NaHCO3 was added to the reaction mixture in order to
neutralize the HCl formed. The synthetic process for the formation of the Schiff
base and the vicinaldioxime is shown in Scheme 1.
The elemental analyses of 1, 2, and its metal derivatives were found to agree
with their constitutions. In the IR spectrum of 1, stretching vibrations for NH2 were
1
observed at 3300±3350 cm . The band due to the C=N stretching was observed at
1
1650 cm . The O±H, C=N, and N±O vibrations which belong to 2 are observed at
1
3200, 1650, and 950 cm .
In the 1H NMR spectrum of 1, a singlet at ꢁ ˆ 5.65 ppm for the aromatic amine
protons is observed. After its reaction to 2, this singlet disappears, and a new signal
is observed at ꢁ ˆ 10:17 ppm which can be assigned to the NH protons in the
neighbourhood of the two oxime groups. On the other hand, a resonance at
ꢁ ˆ 11:4 ppm was found after the reaction with E,E-dichloroglyoxime indicating
that the new OH protons belong to the oxime groups. The N±OH and NH protons
were also identi®ed by D2O exchange.
Trinuclear complexes were obtained with Cu(II) (3), Ni(II) (4), Co(II) (5), and
Pd(II) (6). For each ligand, one metal ion is coordinated to two aza and two oxa
atoms of each ligand, whereas the third metal ion is coordinated by the N,N0 atoms
Scheme 1

A New vic-Dioxime Ligand
177
Fig. 1. Formula of compunds 3±6 (M ˆ Cu, Ni, Co, Pd, respectively)
of each oxime group in the two ligand molecules (Fig. 1). The IR spectra of all
trinuclear complexes were very similar to those of 2 except for the disappearance
1
of the OH stretching frequencies. Weak bands around 1700 cm indicate O±
HÁ Á ÁH bridges, whereas the shift of the C=N vibrations to lower wavenumbers is a
consequence of N,N0-chelation in vicinal dioxime complexes.
In the NMR spectrum of the nickel complex 4, the hydrogen bridging protons
were observed as a single deuterium exchangeable peak at 16.7 ppm as
encountered in similar compounds [9,11]. The signals from the NH protons of
the Ni and Pd complexes 4 and 6 appeared at 10.3 and 10.25 ppm and disappeared
upon addition of D2O, indicating that one metal ion in each ligand was coordinated
two aza and two oxa atoms of each ligand. No signals attributable to OH groups in
the trinuclear complexes were present.
The tetranuclear uranyl complex 7 was obtained by starting with any ratio of the
ligand and the metal salt. In this complex, one uranyl ion is linked to the phenolic
OH and to the aza groups of each ligand, whereas the third and the fourth uranyl ions
are coordinated through one nitrogen and one oxygen atom of each dioxime group in
the two ligand molecules [14] (Fig. 2). The IR spectrum was also consistent with this
Fig. 2. Formula of compound 7

178
E. Hamuryudan et al.
1
structure. A strong band around 900 cm is characteristic for v(O=U=O) vibrations.
The 1H NMR spectrum of 7 showed two signals for the N-OH protons at ꢁ ˆ 11:37
and 11.15 ppm and for the NH protons at ꢁ ˆ 9:41 and 9.14 ppm. This can be
attributed to the magnetic anisotropy of the uranyl ion as discussed in relation to
carboxylate and amine complexes [16]. The uranyl ion enhances the chemical shift
difference between non-equivalent protons. This effect is similar to increasing the
NMR observing frequency by a few orders of magnitude [17].
The electronic spectra of all complexes showed an intense absorption around
400 nm which was assigned to charge-transfer transitions. However, d-d transitions
could not be detected.
Experimental
IR spectra were recorded on a Mattison 1000 FTIR spectrophotometer using KBr pellets; the
electronic absorption spectra were obtained on a Unicam UV2 spectrophotometer. Elemental analysis
was performed by the Instrumental Analysis Laboratory of the Tubitak Marmara Research Centre.
The results were in satisfactory agreement with the calculated values (C, H, N, metal). Proton NMR
spectra were recorded on a Bruker 200MHz spectrometer. anti-Dichloroglyoxime was prepared
according to Refs. [18,19]. All other reagents and solvents were obtained from commercial suppliers.
1-Amino-8-salicylideneiminonaphthalene (1; C17H12N2O)
A solution of 0.75 g 1,8-diaminonaphthalene (4.7 mmol) in 10 cm3 absolute ethanol was added
dropwise to a solution of 0.99 cm3 salicylaldehyde (9.4 mmol) in 15 cm3 absolute ethanol under an
N2 atmosphere at 60±65ꢀC. The reaction mixture was stirred for 2 h at the same temperature, and a
pale yellow precipitate was obtained which was ®ltered off, washed with H2O and cold ethanol, and
dried with cold diethyl ether.
Yield: 0.725 g (59%); m.p.: 186ꢀC; IR (KBr): ꢂ ˆ 3350±3300 (ꢂN±H), 3250 (ꢂOH), 3060±3035
1
(ꢂCH-arom), 1650 (ꢂC=N) cm 1; H NMR (DMSO-d6, ꢁ, 200 MHz): 13.30 (s, OH, D-exchangeable),
8.70 (s, CH=N), 7.60-6.41 (m, 10Harom), 5.65 (s, NH2, D-exchangeable) ppm.
N,N0-Bis-(8-salicylideneimino-1-naphthyl)-diaminoglyoxime (2; C36H28N6O4)
A solution of 0.136 g anti-dichloroglyoxime (0.86 mmol) in 6 cm3 absolute ethanol was added
dropwise to a solution of 0.45 g 1 (1.7 mmol) in 35 cm3 absolute ethanol which also contained 0.8 g
sodium hydrogen carbonate (9.5 mmol) at 30±35ꢀC. After the reaction mixture was stirred at this
temperature for 24 h it was ®ltered. The ®ltrate was poured into 300 cm3 ice-water. The dark yellow
precipitate was ®ltered off and washed with H2O and cold ethanol. The crude product was
chromatographed on silica gel (eluted with CHCl3: CH3OH ˆ 20:1). The compound is soluble in
3
common solvents (e.g. methanol, aceton) up to concentrations of 4.1Â10 2 mol dm
.
Yield: 0.180 g (35%); m.p.: 116±119ꢀC; IR (KBr): ꢂ ˆ 3350 (ꢂN±H), 3200 (ꢂOH), 3050±3020
1
(ꢂCH-arom), 1650 (ꢂC=N), 950 (ꢂN±O) cm
;
1H NMR (DMSO-d6, ꢁ, 200 MHz): 12.05 (s, OH,
D-exchangeable), 11.40 (s, N±OH, D-exchangeable), 10.17 (s, N±H, D-exchangeable), 9.11 (s,
CH=N), 7.60-6.41 (m, 20Harom) ppm.
Bis-(salicylideneiminato-copper-1-naphthyl)-diaminoglyoximato-copper) (3; C72H50N12O8Cu3)
To a solution of 0.24 g 2 (0.39 mmol) in 20 cm3 ethanol was added a solution of 98 mg CuCl2 Á 2H2O
(0.58 mmol) in 10 cm3 ethanol. The mixture was heated on a water bath at 30±40ꢀC for 3 h; during

A New vic-Dioxime Ligand
179
this time the colour of the solution turned dark, and the brown-green complex was precipitated. The
product was ®ltered off, washed with water, ethanol, and diethyl ether, and dried in vacuo.
Yield: 0.17 g (62%); m.p.: >250ꢀC; MS (FAB): m/z ˆ 1401.5 [M‡1]; IR (KBr): ꢂ ˆ 3375 (ꢂN±H),
1
3055±3025 (ꢂCH-arom), 1720 (ꢂO±HÁ Á ÁO), 1610 (ꢂC=N), 960 (ꢂN±O) cm
.
Bis-(salicylideneiminato-nickel-1-naphthyl)-diaminoglyoximato-nickel (4; C72H50N12O8Ni3)
The reddish brown complex was prepared following the same procedure as described for the
preparation of 3 starting from 0.24 g 2 (0.39 mmol) and 0.138 g NiCl2 Á 2H2O (0.58 mmol).
Yield: 0.110 g (40%); m.p.: > 250ꢀC; IR (KBr): ꢂ ˆ 3300 (ꢂN±H), 3050-3025 (ꢂCH-arom), 1750
1
(ꢂO±HÁ Á ÁO), 1600 (ꢂC=N), 960 (ꢂN±O) cm 1; H NMR (DMSO-d6, ꢁ, 200 MHz): 16.73 (s, O±HÁ Á ÁO,
D-exchangeable), 10.30 (s, N±H, D-exchangeable), 9.03 (s, CH=N), 7.82-6.23 (m, 40Harom) ppm.
Bis-(salicylideneiminato-cobalt-1-naphthyl)-diaminoglyoximato-cobalt (5; C72H50N12O8Co3)
The dark brown complex was prepared following the same procedure as described for the
preparation of 3 starting from 0.24 g 2 (0.39 mmol) and 0.138 g CoCl2 Á 6H2O (0.58 mmol).
Yield: 0.180 g (66%); m.p.: > 250ꢀC; IR (KBr): ꢂ ˆ 3350 (ꢂN±H), 3060-3027 (ꢂCH-arom), 1700
1
(ꢂO±HÁ Á ÁO), 1605 (ꢂC=N), 960 (ꢂN±O) cm
.
Bis-(salicylideneiminato-palladium-1-naphthyl)-diaminoglyoximato-palladium
(6; C72H50N12O8Pd3)
A mixture of 0.102 g PdCl2 (0.57 mmol) and 66 mg NaCl (1.14 mmol) was dissolved in 40 cm3
ethanol. The solution was stirred at 70ꢀC until the PdCl2 was dissolved completely. A solution of
0.240 g 2 (0.38 mmol) in 209 cm3 ethanol was added to this Na2PdCl4 solution, and the procedure
described above for 3±5 was followed.
Yield: 0.170 g (56%); m.p.: >250ꢀC; IR (KBr): ꢂ ˆ 3370 (ꢂN±H), 3062-3031 (ꢂCH-arom), 1730
;
1H NMR (DMSO-d6, ꢁ, 200 MHz): 10.25 (s, N±H,
1
(ꢂO±HÁ Á ÁO), 1600 (ꢂC=N), 960 (ꢂN±O) cm
D-exchangeable), 9.01 (s, CH=N), 8.07-6.04 (m, 40Harom) ppm.
Bis-(salicylideneiminato-uranyl-1-naphthyl)-diaminoglyoximato-ꢀ-hydroxo-diuranyl
(7; C72H52N12O18U4)
To a solution of 0.120 g 2 (0.19 mmol) in 20 cm3 hot ethanol a solution of 0.161 g UO2(AcO)2 Á 2H2O
(0.38 mmol) in 10 cm3 ethanol was added. The mixture was heated on a water bath for 1 h at 50±
60ꢀC. The color of the solution became dark, and the brown complex precipitated. The precipitate
was ®ltered off, washed with hot and cold ethanol and diethyl ether, and dried in vacuo.
Yield: 0.072 g (31%); m.p.: > 250ꢀC; IR (KBr): ꢂ ˆ 3350 (ꢂN-H), 3061-3033 (ꢂCH-arom), 1640
;
1H NMR (DMSO-d6, ꢁ, 200 MHz): 11.37-11.15 (s, N-OH,
1
(ꢂC=N), 900 (ꢂO=U=O) cm
D-exchangeable), 9.41±9.14 (s, N-H, D-exchangeable), 9.20 (s, CH=N), 8.12-6.57 (m, 40Harom),
3.65 (s, ꢀ-OH, D-exchangeable)ppm.
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Received June 28, 1999; Accepted (revised) September 18, 1999